normal slider that will change the transparency of a layer
idea behind this one is say for colour theming, you could have 3 layers r,g,b (which could have transparency already applied i.e layer is already at 30% transparency)
Xion could then have 3 sliders for R,G,B layers, this would provide so much scope for colour theming for skins and avoid the need to package multiple psds within a skin
this could be implemented in a few ways, here's the 2 obvious ways, I think for global use within Xion option B would be the best route to go down

A. Let the user implement the 3 sliders into his skin and the corresponding r,g,b layers
B. Xion would control the R,G,B values, these could then be saved for last settings used for example, perhaps with a small slider section for R,G,B in the Settings tab of cfg panel
All the user would then need to add is R,G,B layers (could have multiple r,g,b layers depending on skin design,layer setup, with ids)
colour theming is big stuff within media player skins imo, that appeals to the broadest user base, people like customising their stuff
this would also mean that for example to change colours on different layer bases skinners could even put 1 or 2 of each type of layer within a skin to force specific colours based on colour science, for example triadic colour scheme, if you set 3 different layers with the colours from triadic group then the r,g,b sliders would keep the triadic relationship within the skin colours allowing for some cool stuff

slider that will use anim layer set for both volume and progress which responds to user dragging/movement perhaps with % movement for say 5/10 pixel cells for example

another sort of workaround to multiple colour themes would be to use the colour changer setup as Cliff posted but use this for RGB layers rather than just set colours

this would mean you could have 3 buttons that loop through an animation set and have various transparencies of each R, G , B layer
so say your Red layer is already @ 30% transparency (but set as a flattened layer @ 100%), you could have 10 layers with 10% transparency increments from 0 to 100
your button would cycle thru the red layer animation set and thus change the transparency of any red layers i.e. you would assign the same ID to multiple red layers for example id(red)

so you could structure your layers that dont overlap with seperate r,g,b layers or have a global r,g,b layer over the whole lot etc...

this would give as many colour themes for as many transparency layers you put in

Hmm yeah. The code is all there, I just have it all disabled. I'll enable again and see if its working. I think I ran into some issues with it and wasn't able to continue to get it to work at the time.

It's not 100% what you've asked for above, i.e. with settings window, etc. So its essentially option A. I have some other plans for future though, don't worry

What it does give you though are the sliders that can control the transparency of any other layer (other than themselves). If you add a svst keyword onto the layer you're linked to, it will remember its transparency for next time.

Should be good to give you some more options anyway. I have a few other ideas for the future of this, however I want to get a new public release out before I take on that time consuming task.